[Zero Tolerance]

IT

Used to refer to that one previously mentioned. Used of a nonhuman entity; an animate being whose sex is unspecified, unknown, or irrelevant; a group of objects or individuals; an action; or an abstraction: polished the table until it shone; couldn't find out who it was; opened the meeting by calling it to order.
Used as the subject of an impersonal verb: It is snowing.

Used as an anticipatory subject or object: Is it certain that they will win?
Used as an anticipatory subject to emphasize a term that is not itself a subject: It was on Friday that all the snow fell.
Used to refer to a general condition or state of affairs: She couldn't stand it.
Used to refer to a crucial situation or culmination: This is itthe rivals are finally face to face. That's it! I won't tolerate any more foolishness.
Informal. Used to refer to something that is the best, the most desirable, or without equal: He thinks he's it. That steak was really it!